1. Field of the Invention
The present invention relates to an insulator pressure-cut connector terminal for connecting a core conductor of a wire to a connector terminal by pressure-fitting the wire into at least one insulator cutting open slot formed in a cutter plate of the connector terminal, without stripping the insulating cover material from the wire, and in particular to an insulator pressure-cut connector terminal suitable for use in connecting a large-diameter wire thereto.
2. Description of the Prior Art
Recently, wire insulator pressure-cut connector terminals (referred to as pressure-cut terminals, hereinafter) have been widely used to improve the productivity in the assembly process of automotive vehicles, for instance, because insulator covered wires (referred to wires, hereinafter) can be connected to the pressure-cut terminal by simply pushing the wire to at least one slot for cutting the wire insulator in such a condition that the core conductor of the wire is securely brought into contact with the slot formed n a cutter plate of the pressure-cut terminal.
In the pressure-cut terminal, a flat plate is formed into a box shape; two opposing cutting open slots are formed in two opposing cutter plates of the box, respectively; and an insulated wire is pressure fitted into the open slots for connection of the wire conductor with the connector terminal.
In the conventional pressure-cut terminal, however, when a relatively large-diameter wire is pressure-fitted into the cutting open slots, there exists a problem in that the cuter plate or plates are easily deformed, and therefore the contact reliability between the wire conductor and the contact terminal is deteriorated.
To overcome the above-mentioned problem, a wire insulator pressure-cut connector terminal reinforced by two reinforcing surfaces has been proposed, as disclosed in U.S. Pat. No. 4,575,173.
FIG. 1(A) shows a perspective view of the above-mentioned prior-art pressure-cut terminal, and FIG. 1(B) is an development elevation thereof. With reference to FIGS. 1(A) and (B), the connector terminal is roughly formed with a base plate portion 1 and a box portion 2. The box portion 2 is formed with two opposing side surfaces 3a and 3b bent upright from the base plate portion 1, two cutter plate portions 4a and 5a extending from the side surface 3a and bent inward at right angles with respect to the side surface 3a, two other cutter plate portions 4b and 5b extending from the side surface 3b and also bent inward at right angles with respect to the side surface 3b, and two reinforcing surfaces 6 and 7 extending from the cutter plate portions 4a and 5b and further bent inward at right angles with respect to the cutter plate portions 4a and 5b. Further, four open wire cutting slots 8a, 9a, 8b and 9b are formed in the four cutter plate portions 4a, 5a, 4b and 5b, respectively, into each of which an insulator wire W is pressure fitted for connection of a wire conductor to the pressure-cut terminal.
In the above-mentioned prior-art pressure-cut terminal, since the two reinforcing surfaces 6 and 7 are additionally formed, although it is possible to increase the rigidity of the open slots 4a, 5a, 4b and 5b, there still exists a problem in that the cutter plate portions tend to be deformed during the bending process, as shown by solid lines in FIG. 1(C) and therefore the rigidity of the cutter plate portions are not sufficiently high, so that the cutter plate portions are easily further deformed when the wire is pressure fitted into the open slots.
The causes of the above-mentioned deformation of the cutter plate portions may be due to the following fact:
The pressure-cut terminal shown in FIG. 1(A) can be formed by bending a flat blank plate material formed into a development elevation as shown in FIG. 1(B). In FIG. 1(B), the two side surface portions 3a and 3b are formed roughly in symmetry with respect to the base plate 1; the four opposing cutter plate portions 4a, 5a, 4b and 5b extend from the side surface portions 3a and 3b, respectively; and further two reinforcing surfaces 6 and 7 extend from the cutter plate portion 3a, respectively.
With reference to FIGS. 2(A) to 2(E), the steps of forming each box portion 2 will be described hereinbelow. FIG. 2(A) shows a side view of a blank plate material when seen from A in FIG. 1(B). In the first step, both the reinforcing surface portions 6 and 7 are bent at a small angle by a first mated die as shown in FIG. 2(B); in the second step, the two opposing cutter plate portions 4a and 5a are bent at about 45 degrees as shown in FIGS. 2(C) by a second die; in the third step, the same two opposing cutter plate portions 4a and 5a are further bent at right angles as shown in FIG. 2(D) by a third die; and in the final step, the reinforcing surface portions 6 and 7 are bent at right angles with respect to the two opposing cutter plate portions 4a and 5a as shown in FIG. 2(E) by a fourth die.
In the above-mentioned bending process, since there inevitably exist some spaces or hollow cavities such as C.sub.1, C.sub.2 and C.sub.3 between the second to fourth mated dies, it has been rather difficult to accurately bend the blank flat plate into a box shape as shown in FIG. 2(E), so that the corner of the cutting plate portion 4a or 5a may be deformed into an undesirable shape as shown in FIG. 1(C).
In summary, in the prior-art pressure-cut terminal, there exists a problem in that the rigidity of the open slots in the cutter plate portions is not sufficiently high and therefore the cutter plate portions are easily deformed when a relatively large-diameter insulated wire is pressure fitted into the open slot. In addition, where two reinforcing portions 6 and 7 are further formed, it has been difficult to form the pressure-cut terminal into an accurate shape and therefore to increase the rigidity of the pressure-cut terminal sufficiently high.